The accident happened off the coast of Virginia Beach on Friday, the FBI's national press office announced in a statement Sunday. No other details were given and the cause is under investigation.

The special agents were identified as Christopher Lorek, 41, and Stephen Shaw, 40. Lorek joined the FBI in 1996 and is survived by a wife and two daughters, 11 and 8. Shaw joined in 2005 and is survived by a daughter, 3, and son, 1.

"We mourn the loss of two brave and courageous men," Director Robert Mueller said in the statement. "Like all who serve on the Hostage Rescue Team, they accept the highest risk each and every day, when training and on operational missions, to keep our nation safe. Our hearts are with their wives, children, and other loved ones who feel their loss most deeply. And they will always be part of the FBI Family."

The Hostage Rescue Team is part of the Critical Incident Response Group based at Quantico in northern Virginia. Most recently, members of the team successfully rescued a 5-year-old boy from a small underground bunker where he was being held hostage by a 65-year-old man. The man was killed by agents.

Trained in military tactics and outfitted with combat-style gear and weapons, the group was formed 30 years ago in preparation for the 1984 Olympics in Los Angeles. The team is deployed quickly to trouble spots and provides assistance to local FBI offices during hostage situations. It has participated in hostage situations more than 800 times in the U.S. and elsewhere since 1983.